Skywatch Line for Friday, January 4 through Sunday, January 6, 2019

This is Dudley Observatory’s Skywatch Line for Friday, January 4 through Sunday, January 6, written by Sam Salem.

On Friday, the Sun rises at 7:27am and sets at 4:35pm; the waning crescent Moon rises at 6:06am and sets at 3:38pm. The new Moon occurs on Saturday at 8:28pm. 2019’s first new Moon will pass between the Earth and Sun to stage a partial eclipse of the Sun. It happens on the night of January 5 for time zones in the Americas, thus we won’t see it. The partial eclipse will be visible from China, Korea, Japan, Russia, North Pacific Ocean and Alaska’s Aleutian Islands.

Mars, at magnitude 0.5, stands out readily from the faint stars populating the early evening sky. Mars, in constellation Pisces, sets around 11:15pm. In a telescope, Mars is gibbous and quite small, about 7½ arc-seconds from pole to pole. The rest of the solar system action takes place at dawn. Venus, at magnitude –4.6 in constellation Virgo, clears the southeast horizon at about 3:40am. In a telescope, Venus is almost half sunlit. Venus is at greatest elongation from the Sun on Sunday. Elongation is the angle observed from the Earth between the direction to the Sun and the direction to the planet. From this point on Venus will appear to gradually drift sunward. The brilliant planet will remain standing out in the morning sky through to summer. Venus is an inferior planet that orbits the Sun inside of Earth’s orbit. Venus swings out to its greatest elongation as a “morning star” this Sunday going 47 degrees west of the Sun on the sky dome.

Jupiter, at magnitude –1.8, rises at around 5:10am, lower left of brighter Venus. By the time twilight brightens the sky, Jupiter has climbed to an altitude of nearly 14 degrees. Look closer to Jupiter’s lower right for orange Antares. Mercury, at magnitude –0.4, is at the tail end of its current apparition. Mercury is getting lower in the dawn rising at about 6:30am. It sits lower left of brighter Jupiter, which in turn is lower left of even brighter Venus. Mercury and Jupiter move farther apart every day. To see Mercury you’ll need an unobstructed horizon to the east-southeast.

Dog Star, Sirius, reaches its highest point in the sky around midnight every New Year’s Eve. It rises 4 minutes earlier each passing night. Find Sirius below constellation Orion, very low in the southeast. Sirius is easy to see because it’s so bright and because the three prominent Belt stars in the constellation Orion always point to it. Sirius flashes different colors as it rises near the horizon. The prismatic effects of Earth’s atmosphere cause this optical illusion. Look for Sirius and the faint star cluster near it. It’s the lovely star cluster M41. This cluster lies about four degrees, south of Sirius. M41 is sometimes also called the Little Beehive, after the other famous Beehive star cluster (M44), also an open cluster, in the constellation Cancer. In clear, dark skies, M41 is visible to the naked eye. It has an apparent magnitude of 4.5 and lies at an approximate distance of 2,300 light years from Earth. M41 can be seen in the same binocular field with Sirius and Nu-2 Canis Majoris, an evolved orange giant with a visual magnitude of 3.95. The cluster forms a triangle with the two stars. The cluster is relatively loose and can be resolved in a small telescope. It is best observed at low magnifications. Small telescopes resolve about 50 stars, while 6-inch and 8-inch telescopes show many more fainter members. The best time of year to observe M41 is in the months of December, January, and February. M41 occupies an area of 38 arc-minutes in apparent diameter, roughly the size of the full Moon.

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